During recent years one-dimensional pulse echo ultrasonic techniques have proven to be extremely useful in cardiac diagnosis. A one-dimensional system, however, only measures distances to structures lying along a single straight line. Cardiac anatomy is therefore not so easily defined as with a two-dimensional system which simultaneously measures distances along many straight lines comprising a plane. Several systems have been described for obtaining two-dimensional echo cardiograms. None, however, has combined electronic control of sector width and scan linearity with the advantages of a high sensitivity, narrow beam transducer, real time imaging, and a simple method for controlling the section of the heart being viewed. A serious limitation of the presently available electro-mechanical sector scanners is the lack of electronic control of sector width and scan linearity.
In the course of a preliminary search, the best prior art found relating to the subject matter of the present invention appears to comprise the following U.S. Pat. Nos.
Eggleton et al, 3,817,089
Lee at al, 3,893,449
Ranalli et al, 3,864,668
Wilcox, 3,881,466
Takemura, 3,927,661
Kossoff, 3,939,696
Eggleton, 3,955,561
Eggleton et al, 3,974,826
The following publications also appear to represent the known state of the art:
Fiegenbaum, "Clinical Applications of Echocardiography, Prog. Cardiovase Dis.," 14: 531, 1972.
Popp and Harrison, "Ultrasound in the Diagnosis and Evaluation of Therapy of Idiopathic Hypertrophic Subaortic Stenosis," Circulation, 40: 905, 1969.
Henry and Epstein, "Aymmetric Septal Hypertrophy ; Echocardiographic Identification of Pathognomic Anatomic Abnormality of IHSS," Circulation, 47: 225, 1973.
Griffith and Henry, "A Sector Scanner for Real Time Two-dimensional Echocardiography," Circulation 49: 1147, 1974.
Flaherty, Clark and Walgren, "Simultaneous Fluoroscopic and Rapid Scan Ultrasonic Imaging," Dig. Int. Conf. Med. Biol. Eng., 7; 221, 1967.
Thurston and Von Ramm, "A New Ultrasound Technique Employing Two-Dimensional Electronic Beam Steering," in Acoustical Holography, Vol, 5, Plenum Publishing Corp., New York, 1974.
Perhaps the most pertinent of the prior systems is that disclosed by Griffith et al; however this prior system does not provide a sufficient linear sector sweep and thus requires the use of small sector angles. Accordingly, the need exists for a system of the type desired below.